But now two trials, including one involving the supply of nitrous oxide at a Derbyshire festival, have ended abruptly after it was argued the substance is exempt from new legislation.

The Home Office says it will continue to prosecute those who sell nitrous oxide, despite the collapse of the first contested cases under new laws.

A man was tried at Southwark Crown Court on Wednesday for intending to supply nitrous oxide at a music festival in Derbyshire.

But prosecuting barrister Adrian Fleming told the court that the Crown’s own expert witness, Professor Philip Cowen, “is expressing the firm view that nitrous oxide, as the legislation is currently worded, is an exempt substance”.

Laughing gas, or nitrous oxide, is used most commonly to provide pain relief during dentistry and childbirth.